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[multicast] wire up softnpu backend to multicast table ops#242

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zl/softnpu-with-mcast
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[multicast] wire up softnpu backend to multicast table ops#242
zeeshanlakhani wants to merge 1 commit intomulticast-e2efrom
zl/softnpu-with-mcast

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@zeeshanlakhani zeeshanlakhani commented Mar 24, 2026

This wires up the softnpu ASIC backend to support multicast end-to-end by translating DPD's sidecar.p4 table operations into sidecar-lite.p4's simplified P4 pipeline.

AsicMulticastOps

We replace the stubbed AsicMulticastOps implementation (which returned "OperationUnsupported" for group creation and port addition with in-memory group tracking via McGroupData, following the tofino_stub pattern.

Group membership is used by the table translation layer to build port bitmaps for sidecar-lite's Replicate extern. Ports >= 128 are rejected at add time to match sidecar-lite's 128-bit bitmap width.

Table translation (asic/src/softnpu/table.rs)

We map sidecar.p4 table names to sidecar-lite equivalents and translate action parameters where the designs differ for emulation.

All multicast action arms are gated with #[cfg(feature = "multicast")].

References

This wires up the softnpu ASIC backend to support multicast end-to-end by
translating DPD's sidecar.p4 table operations into sidecar-lite.p4's
simplified P4 pipeline.

## AsicMulticastOps

We replace the stubbed AsicMulticastOps implementation (which returned
"OperationUnsupported" for group creation and port addition with in-memory group
tracking via McGroupData, following the tofino_stub pattern.

Group membership is used by the table translation layer to build port
bitmaps for sidecar-lite's Replicate extern. Ports >= 128 are
rejected at add time to match sidecar-lite's 128-bit bitmap width.

## Table translation (asic/src/softnpu/table.rs)

We map sidecar.p4 table names to sidecar-lite equivalents and translate
action parameters where the designs differ for emulation.

All multicast action arms are gated with #[cfg(feature = "multicast")].

## References

- [softnpu #183](oxidecomputer/softnpu#183)
- [propolis #1093](oxidecomputer/propolis#1093)
- [p4rs #240](oxidecomputer/p4#240)
- [sidecar-lite #152](oxidecomputer/sidecar-lite#152)
- tokio: 1.50 (due to softnpu)
- oxide-tokio-rt: 0.1.3 (following-up from tokio's move to 1.50)
@zeeshanlakhani zeeshanlakhani force-pushed the zl/softnpu-with-mcast branch from a3f94ef to abf35dd Compare March 30, 2026 05:54
@zeeshanlakhani zeeshanlakhani changed the title [multicast] Wire softnpu backend to multicast management protocol [multicast] wire up softnpu backend to multicast table ops Mar 30, 2026
@zeeshanlakhani zeeshanlakhani marked this pull request as ready for review March 30, 2026 06:30
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